#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
int main()
{
	int n = 100;
	int i = 1;
	double sum = 0.0;
	int flag = 1;
	for (i = 1; i <= n; i++)
	{
		sum += flag*(1.0 / i);
		flag = -flag;
	}
	printf("%lf", sum);
	return 0;
}
